Although considerable effort has been made over the years to define the role of the spleen in bacterial susceptibility, there remains a number of controversial postulates. In no area in this more apparent than following splenectomy in children. While most of these splenectomized patients have associated hemotologic pathology which may contribute to this increased susceptibility, there have been increased incidents where fulminating pneumococcal and meningococcal infections follow splenectomies for trauma. This syndrome appears related primarily to pediatric patients. It is the objective of this study to develop an animal model for the study of the effect of splenectomy on the pulmonary bacterial susceptibility in pediatric patients. Sprague-Dawley rats, bred and raised in our own laboratory, will be divided into control, sham, splenectomized with autotransplant groups at 3 weeks of age and 12 weeks of age. They will be subjected to an aerosol pneumococcal bacterial challenge 6 days and 21 days following surgery. Evaluation will be by mortality, pathology, and lung bacterial clearance using quantitative bacterial techniques.